1. Field of the Invention
This invention relates generally to the field of resonance heating of gas for propellant and oxidizer ignition and, more particularly, to a system for resonance heating of oxygen employing a ceramic resonance cavity and hot gas bleed withdrawal for generating an ignition torch.
2. Description of the Related Art
Resonance ignition is based on a phenomenon known as gasdynamic resonance, wherein supersonic, underexpanded flow is axially directed from a supersonic nozzle 2 at a tube with a closed end, referred to as a resonance cavity 4, causing an oscillating detached bow shock to form in a chamber 6 upstream of the entrance to the cavity as shown in FIG. 1. Gas then exits the chamber through a restricting orifice 8. Reflected shocks from the end of the resonance cavity couple and reinforce the detached bow shock, interacting with the flow within the tube such that the successive cycles of shocks cause the formation of a series of unstable zones of elevated pressure within the tube. These zones can produce temperature increases up to ˜2000 R for certain gases. The physical criteria for the interaction are defined by “d” the diameter of the supersonic inlet nozzle, “G” the distance between the nozzle throat and the mouth of the resonance cavity and “DMC” is the diameter of the throat of the restriction orifice.
Gasdynamic resonance was first described by Hartmann in 1931, who was investigating acoustics and overlooked the associated temperature increase. The term resonance tube was first coined by Sprenger in 1954, who rediscovered the phenomenon and observed the conditions that affect temperature increase (Sprenger once demonstrated the temperature increase by directing supersonic, underexpanded flow at a blind cavity in a piece of wood, which would catch fire after a very brief period). Theories for the temperature increase were put forth in 1959 by Wilson and Resler, and in 1960 by Shapiro. Shapiro, A. H., “On the Maximum Attainable Temperature in Resonance Tubes,” Journal of the Aero/Space Sciences, 66–67, January 1960. The pressure flowfield was described by Thompson in 1960 and his student Kang in 1964. Thompson, P. A., “Jet-Driven Resonance Tube,” AIAA Journal 2, 1230–1233 (1964). In 1970, Pavlak and his student McAlevy noted that using tapered tubes decreased the time to elevate the temperature of the gas. McAlevy III, R. F. and Pavlak, A., “Tapered Resonance Tubes: Some Experiments,” AIAA Journal 8, 571–572 (1970). All of this initial work was academic in nature, however, and did not investigate applications of the phenomena to existing technology. In 1967, Conrad and Pavli of the NASA Lewis Research Center suggested using gasdynamic resonance to ignite liquid rocket engines. This work was followed by an investigation by Phillips and Pavli in 1971 to determine what geometric parameters influenced the maximum attainable temperature and response time. Phillips, B. R. and Pavli, A. J., “Resonance Tube Ignition of Hydrogen-Oxygen Mixtures,” NASA TN D-6354, May 1971. At around the same time (1968–1974), Vincent Marchese of the Singer Company investigated applying the concept to ignition of small solid rockets using a hand-powered pneumatic pump, under various contracts with the U.S. Army, NASA, and the Ballistic Missile Defense Organization. Marchese, V. P., “Development and Demonstration of Flueric Sounding Rocket Motor Ignition,” NASA CR-2418, June 1974. Marchese used the term “pneumatic match” to refer to the resonance igniter, and performed an extensive parametric study of the resonance cavity geometry.
More recently, a “Passive Self-Contained Auto Ignition System,” has been disclosed in U.S. Pat. No. 5,109,669, issued May 5, 1992 to Donald Morris and Gary Briley. Additionally, U.S. Pat. No. 6,272,845 B2 entitled “Acoustic Igniter and Ignition Method for Propellant Liquid Rocket Engine” issued Aug. 14, 2001 to Khoze Kessaev, Vasili Zinoviev, and Vladimir Demtchenko.
It is desirable to employ the simplicity of resonance heating for an ignition system without requiring cooling of the resonance cavity. Further, it is desirable to employ oxygen as the resonating fluid to allow use with various fuels including liquid fuels.